The Orville Season Two - Thoughts?

Umbran

Mod Squad
Staff member
I finally got around to watching the final episode.

It was like someone in the writer's room said, "Hey, waitaminute. We are a Trek homage show. If we haven't made science-literate geeks have at least one moment of abject apoplexy this season, we aren't doing our job!"

Other than my speachless gesticulating at the screen for a few moments, it was decent.
 

Umbran

Mod Squad
Staff member
But the fact that they can "see" what is going on inside the black hole is super dumb: if their sensors can accomplish that inside the black hole they should be able to accomplish it outside.
Nope. That part is pretty much okay. Light falling in to a black hole does not *stop* at the event horizon. It falls in, and could be detected on the inside. Okay, technically it gets blue-shifted to gamma rays on the way in, but that's the *least* of the problems with the black hole bit.

The fact that they made such a point about the intense pressure under seven miles of ocean made ignoring the pressure from inside a black hole even that much more painful to stomach.
There isn't any particular pressure inside a black hole. It is still a vacuum, for one thing. And the space inside the event horizon is just like the space outside it. The curvature increases as you head toward the singularity, but there's no discontinuity at the event horizon that suddenly increases pressure.
 

Kaodi

Adventurer
Nope. That part is pretty much okay. Light falling in to a black hole does not *stop* at the event horizon. It falls in, and could be detected on the inside. Okay, technically it gets blue-shifted to gamma rays on the way in, but that's the *least* of the problems with the black hole bit.
This does not quite make sense to me. For them to "detect" the light falling towards the centre some would still have to escape towards them, would it not? But the "event horizon" should not really be a singular place, should it? Once you are inside it is basically event horizons all the way down, is it not? If light cannot escape at x distance then there is no way it can escape at x - n distance.
 

Nagol

Unimportant
Nope. That part is pretty much okay. Light falling in to a black hole does not *stop* at the event horizon. It falls in, and could be detected on the inside. Okay, technically it gets blue-shifted to gamma rays on the way in, but that's the *least* of the problems with the black hole bit.



There isn't any particular pressure inside a black hole. It is still a vacuum, for one thing. And the space inside the event horizon is just like the space outside it. The curvature increases as you head toward the singularity, but there's no discontinuity at the event horizon that suddenly increases pressure.
There would be tidal stress effects on the hull though, but that would be "pushing out" (actually linear stretching stress as opposed to expansion) as opposed to "pressing in". The ship needs to be designed to support a minimal amount of analogous "pushing out" from air pressure so I could wink at external pressure being a greater risk. It just has to be a *very* big black hole to drop the tidal effect to manageable levels. Who knew a massive black hole was wandering around that section of the galaxy? No one! No one knew!
 

Nagol

Unimportant
This does not quite make sense to me. For them to "detect" the light falling towards the centre some would still have to escape towards them, would it not? But the "event horizon" should not really be a singular place, should it? Once you are inside it is basically event horizons all the way down, is it not? If light cannot escape at x distance then there is no way it can escape at x - n distance.
It's not escaping towards them, they are inside the event horizon so light is falling over them like water in a shower on its way deeper into the hole. The event horizon is the surface of a sphere some distance from the singularity point (the more massive the hole, the farther the surface of the sphere from centre of mass). Nothing is really there other than gravity at sufficient force levels that light can't escape.
 

tomBitonti

Explorer
If they are inside the black hole, then either they are using their faster-than-light drive to keep from falling inwards, or they are falling inwards along with light any any other unlucky matter in their vicinity. (Light would be moving along a geodesic which terminates at the singularity; any normal motion must also terminate at the singularity.)

Just *keeping still*, meaning, keeping at a constant distance from the singularity, requires use of the faster-than-light drive.

In regards to tidal forces, to tell whether the ship and crew are "spaghettified" this: https://en.wikipedia.org/wiki/Spaghettification suggests the following values:

(Solar masses, event horizon radius, "spaghettification" radius")
(10 S, 30 km, 320 km)
(100 S, 300 km, 685 km)
(1000 S, 3000 km, 1462 km)
(10000 S, 30000 km, 3200 km)

The critical radius moves inside of the event horizon somewhere between 100 and 1000 solar masses.

Thx!
TomB
 
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Umbran

Mod Squad
Staff member
It just has to be a *very* big black hole to drop the tidal effect to manageable levels. Who knew a massive black hole was wandering around that section of the galaxy? No one! No one knew!
Oh, their handling of the tidal forces can be explained - we know they can generate gravity (to keep people with feet on the deck, and probably more dynamically to keep crew members from becoming red smears on the bulkheads when they perform high acceleration maneuvers). They just use internal gravity generators to counter the effects.
 

Umbran

Mod Squad
Staff member
If they are inside the black hole, then either they are using their faster-than-light drive to keep from falling inwards, or they are falling inwards along with light any any other unlucky matter in their vicinity. (Light would be moving along a geodesic which terminates at the singularity; any normal motion must also terminate at the singularity.)

Just *keeping still*, meaning, keeping at a constant distance from the singularity, requires use of the faster-than-light drive.
Yep. And, a nod to this would have been a really good way to prevent us from awkwardly gesticulating at the TV in frustration :)
 

Umbran

Mod Squad
Staff member
This does not quite make sense to me. For them to "detect" the light falling towards the centre some would still have to escape towards them, would it not?
Nope.

They are just inside the event horizon, looking out. Photons from outside are falling in at them - they can detect those. There will be some warping of the field of view, but the event horizon does not present a discontinuity. If you are just outside the event horizon, looking around, and then step just inside, the world will look much the same.

But the "event horizon" should not really be a singular place, should it? Once you are inside it is basically event horizons all the way down, is it not? If light cannot escape at x distance then there is no way it can escape at x - n distance.
Pretty much, yes. The event horizon is the *outermost* such position. Which means you can always see things that are farther out from the singularity than you are. You can't look *inwards* and see anything. You always seem to be standing on the surface of a black sphere.
 

tomBitonti

Explorer
Nope.

They are just inside the event horizon, looking out. Photons from outside are falling in at them - they can detect those. There will be some warping of the field of view, but the event horizon does not present a discontinuity. If you are just outside the event horizon, looking around, and then step just inside, the world will look much the same.



Pretty much, yes. The event horizon is the *outermost* such position. Which means you can always see things that are farther out from the singularity than you are. You can't look *inwards* and see anything. You always seem to be standing on the surface of a black sphere.
Is this correct? If one were held still, perhaps, but an infalling observer should still see objects which fell ahead of them. In the infalling frame, the light proceeds outwards. From the perspective of a still frame of reference, the observer would seem to catch up to light emitted by the object which preceded them across the event horizon.

If objects which fell ahead of the observer could not be seen, then physics as we know it would not occur for the observer once they are within the event horizon: Putting the observer's feet closer to the singularity, no nerve signal could be transmitted to reach the observer's brain. Putting the floor beneath the observer's feet closer to the singularity than the observer's feet, no exchange particles could reach outwards from the floor to create contact pressure. I am thinking, all sorts of physical processes would be very different. That is not consistent with the idea that the event horizon could be crossed without notice (aside from tidal effects).

Thx!
TomB
 

Umbran

Mod Squad
Staff member
Is this correct?
I think so. Freyar might correct me. But, light follows geodesics. From the event horizon inwards, there are no geodesics that ever carry you *farther away* from the singularity, iirc. They all spiral inwards to varying degrees. Each time you take a step towards the singularity, there is no going back out.

There may be some exceptions, especially for black holes with high rates of spin. But I'm not near my notes at the moment to check.

If one were held still, perhaps, but an infalling observer should still see objects which fell ahead of them. In the infalling frame, the light proceeds outwards.
There isn't one single infalling frame for all things inside the event horizon. Each thing has its own rest frame. The space is decidedly *not* flat in there, so frames at different distances from the singularity are under acceleration relative to one another, and the acceleration difference will increase as you get closer to the singularity. And at the event horizon, you've already gotten to the point where light of things ahead of you has been red-shifted to infinity. I don't see why that would change when you cross the horizon.

Again, maybe I am forgetting something, and I am not near my notes.
 

tomBitonti

Explorer
I think so. Freyar might correct me. But, light follows geodesics. From the event horizon inwards, there are no geodesics that ever carry you *farther away* from the singularity, iirc. They all spiral inwards to varying degrees. Each time you take a step towards the singularity, there is no going back out.

There may be some exceptions, especially for black holes with high rates of spin. But I'm not near my notes at the moment to check.

There isn't one single infalling frame for all things inside the event horizon. Each thing has its own rest frame. The space is decidedly *not* flat in there, so frames at different distances from the singularity are under acceleration relative to one another, and the acceleration difference will increase as you get closer to the singularity. And at the event horizon, you've already gotten to the point where light of things ahead of you has been red-shifted to infinity. I don't see why that would change when you cross the horizon.

Again, maybe I am forgetting something, and I am not near my notes.
This particular question has bugged me for a while. I don't have a clear answer, just what seems to be necessary for consistency.

Very definitely, there would be perceivable effects of the curvature; that would be tidal effects, and red and blue shifting of light.

What seems necessary is that light can appear to proceed "outwards", but that is only within the frame of the infalling observer. From a frame which is still relative to the singularity, both the observer and the observed light are and must always move towards the singularity.

That seems to be necessary for the transition across the event horizon to not have a dramatic effect. The alternative is a total disconnection (aside from gravitational effects) of anything inside the event horizon from anything closer to the singularity. Normal matter couldn't even exist, as it relies on particle exchange, and that would become impossible in an outward direction.

Thx!
TomB
 

Umbran

Mod Squad
Staff member
This particular question has bugged me for a while. I don't have a clear answer, just what seems to be necessary for consistency.
Did a bit of quick reading from work...

The whole idea of "you could fall in and nothing happens" as you approach a supermassive black hole, is not what it appears. It is really talking about your approach (like, you don't get sphagettified). And there's no discontinuity at the event horizon...

However, after that, things get messy. Fast. It turns out that any choice of coordinate system runs into trouble, and you have to start talking about coordinate-invariant qualities. But then it becomes near impossible to speak about what happens to say, a human's body. You have funny things happen depending on whether you enter traveling in the direction of the hole's spin, or against the spin. Ugly.
 
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Ryujin

Adventurer
Given that they have control of both gravity and inertial, I tend to think of the ship as an independent and closed system.

... until that control fails.
 

tomBitonti

Explorer
Did a bit of quick reading from work...

The whole idea of "you could fall in and nothing happens" as you approach a supermassive black hole, is not what it appears. It is really talking about your approach (like, you don't get sphagettified). And there's no discontinuity at the event horizon...

However, after that, things get messy. Fast. It turns out that any choice of coordinate system runs into trouble, and you have to start talking about coordinate-invariant qualities. But then it becomes near impossible to speak about what happens to say, a human's body. You have funny things happen depending on whether you enter traveling in the direction of the hole's spin, or against the spin. Ugly.
This seems to be on point:

https://web.stanford.edu/~oas/SI/SRGR/notes/SRGRLect10_2007.pdf

Some main points are this, from page 3, regarding a non-rotating case:

This reflects the fact that for the in falling object, it is always in a freely falling frame, an ever shrinking IRF. As the object passes the horizon, nothing significant happens. It doesn’t even notice that it has passed.
That "IRF" in "ever shrinking IRF" is short for "Inertial Reference Frame". Close to the infalling observer, spacetime is still flat: An infalling observer will still see their feet, and locally physics will work as expected.

For the spinning case, page 4 changes the metric, and has:

So our map, so far, looks like any other flat spacetime IRF however here thismust be seen as a patchwork of small local frames. We will examine a series of pointsand rays to find how to represent the shell observer and Schrodinger (far away) coordinates within this map.
So locally we are still OK, but the global picture is a lot more complicated.

Off topic: There is an interesting bit towards the end (page 8) which talks about difficulties of working out quantum gravity:

To explore fluctuations greater than the Planck mass, or equivalently to measure distances shorter than the Planck length Rp, neither general relativity nor quantum field theory can be used alone. We can also get a sense of the energy of the fluctuation and the time limit by going backto the uncertainty relation.

Again, to describe fundamental particles with an energy of the scale of the Planck energy or time intervals less than the Planck time requires a theory of quantum gravity. We can take this time limit as the approximate limit in exploring the initial conditions of the big bang. What this argument suggests is that we can push the separate theories of general relativity and quantum field theory (quantum mechanics united with special relativity) back to a time of about 10-42 s or so. Prior to this time physics is governed by the unknown theory of quantum gravity. If a theory of quantum gravity is developed, the hope is that it will describe the initial conditions of the universe and answer all questions about its development. Hence, such a theory would be enormously powerful. Over the past 50 years it has become clear that such a theory is not going to be easily developed.

What are the difficulties in uniting these two powerful theories? There are several different ways to point out the conflicts. First, it is clear that general relativity needs to have some modification on the extremely small, high energy scale. At the center of black holes and the beginning of the universe, the theory calls for a singularity. This singularity is a point of infinite spacetime curvature and energy density. Such singularities are mathematically unacceptable. However in low curvature, low energy, regions the general theory is an accurate theory. Quantum field theory (the unification of quantum mechanics and special relativity) on the other hand is an accurate theory on short distance, moderately high energy, scales. On the large scale, low energy scale, quantum mechanics transitions to classical mechanics. A transition which is not entirely well understood. There is much work today on this transition regime between quantum mechanics and classical physics.Another problem in bringing together these two theories is the question of what exactly is being quantized. To discuss quantization, first consider classical electromagnetic theory and its quantized form quantum electrodynamics. The process of quantizing the electromagnetic theory replaces the notion of an electromagnetic wave with particles (quanta) which mediate the electric and magnetic forces. The photon is the quanta of EM radiation. Classically it is electromagnetic waves (or electric and magnetic fields) which mediate the forces. This is what is being quantized.(The process is more complicated then simply replacing waves with particles but there is nospace to discuss the details). For general relativity what is to be quantized? Recall that the Einstein equation gives the metric solution for a particular distribution of energy. The metric is the ‘field’ which mediates the gravitational force (we are drawing an analogy to electricity and magnetism, again, there is no gravitational force but the curvature of spacetime). So the quantity to quantize is the metric itself. Or, put another way, spacetime itself must be quantized! This is surely a strange requirement. What does it mean to replace spacetime with quanta (gravitons) which mediate the gravitational force? What do these particles propagate through, since there is no longer a continuum of spacetime? Tying this together with quantum mechanics which employs time and space as parameters to describe the wave functions of the quanta – here being space and time itself. It is somewhat self-referential and causes difficulties in even beginning to construct a theory. Quantum theory relies on a spacetime background, however here we are doing away with such a concept and replacing it with discrete particles.
Thx!
TomB
 

Richards

Adventurer
Hey, if anyone's interested, Dark Horse just came out with the first issue of a new Orville comic book miniseries today. Apparently there will be four issues in all, comprising two different two-part stories. Check your local comic book shop for details.

Johnathan
 

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